The invention relates to tools and procedures, which, in use, form cavities in interior body regions of bones, particularly in vertebrae, for diagnostic or therapeutic purposes.
Certain diagnostic or therapeutic procedures require the formation of a cavity in a bone mass. This procedure can be used to treat any bone, for example, bone which due to osteoporosis, avascular necrosis, cancer, or trauma, is fractured or is prone to compression fracture or collapse. These conditions, if not successfully treated, can result in deformities, chronic complications, and an overall adverse impact upon the quality of life.
For example, as described in U.S. Pat. Nos. 4,969,888, 5,108,404, and 5,827,389, an expandable body is deployed to form a cavity in cancellous bone tissue, as part of a therapeutic procedure that fixes fractures or other abnormal bone conditions, both osteoporotic and non-osteoporotic in origin. The expandable body compresses the cancellous bone to form an interior cavity. The cavity receives a filling material, which provides renewed interior structural support for cortical bone.
U.S. Pat. No. 5,062,845 described a surgical tool for preparing a graft site between opposing vertebra. The tool has a distal end with external dimensions sized to be passed through the patient""s anatomy to a point of entry on the spine. At each incremental extension, the surgeon rotates the handle so that the blades cut out a large chamber equal to the size of the diameter of the extended extendable blades located on the distal end of the tool. After each such cut, the handle is turned to progressively increase the diameter of the cutting edges of blades until a chamber of desired size (up to the diameter of the fully extended blades) is formed. Intermittently, between enlarging the diameter of the cavity, the surgeon may retract the blades and remove the tool to flush the cavity being formed.
U.S. Pat. No. 5,512,037 describes a percutaneous surgical retractor having an outer sleeve with an open beveled configuration and having an angle defining a leading edge on the distal end of the outer sleeve to facilitate percutaneous insertion of the retractor; a blade slidable within said outer sleeve between at least a deployed position extending beyond the distal end of the outer sleeve and a retracted position disposed within the outer sleeve, the blade having a deployable memory curved distal end.
The invention provides new tools and methods for creating cavities in cancellous bone, for example but not limited to vertebroplasty, and for treating these cavities by injecting appropriate treatment materials, i.e., bone paste, cement, autograft, allograft, etc. The tools include a probe that introduces a passageway to the cancellous area, a cannula which expands the hole in the bone and provides a passageway for a tamp or flexible curette to push or tamp back the cancellous structure to form the cavity, and a syringe which fills the cavity with appropriate treatment material. These tools advantageously work together.
The Probe:
The probe is a long slender body with a sharp tip and a handle. The outer diameter of the long slender body is sufficient to fit inside the cannula. The tip of the probe may contain a drilling tip, a sharp point, a serrated edge, or a combination thereof. In a preferred embodiment, the probe has a changeable sharp tip firmly held by a probe sheath that provides strength and gently sloping surfaces useful for wedging or pushing away bone. In another embodiment, the probe and sheath are integrated into a single piece construction. In use, the cannula may be pre-loaded onto the probe so that the handle of the probe need not be removed to insert the cannula. In one embodiment, illustrated in FIGS. 2A and 2B, the probe body has depth markings. These markings can help the physician determine the position of the cannula as it is being placed in the bone. In addition, the markings may also indicate whether the positioning of the cannula is also moving the probe out of the position selected by the physician.
In one embodiment, the handle is detachable from the long slender body so that the cannula may be placed onto the probe after the probe has been positioned in the bone. The detachable handle may be designed to be disposed of after completion of the surgical procedure. For instance, the handle may be fabricated from low cost polymer material, have a simplified attachment mechanism, or both so that replacement of the disposable handle is relatively inexpensive. In one embodiment, the disposable handle is made from plastic material. One advantage of this embodiment is that the plastic would provide radio-lucent to better view the treated area. Fabrication of the handle may be by machining, molding, or any other method. The handle helps provide a better grip and greater control of the probe during its initial positioning. In addition, the handle also may be used to help remove the probe after the cannula is positioned.
Other items described herein also may be designed to be disposable after use. For instance, the handle for the cannula may likewise be made of low-cost polymer material using any suitable fabrication method. Moreover, many of the tools described herein may be designed with a limited or single use in mind. In one embodiment, for instance, the many of the tools in a kit for performing vertebroplasty may be disposed of after completion of the surgical procedure. In a preferred embodiment, the cavity creating tamp is reuseable while the other tools in a kit provided to the surgeon are disposable.
The probe guides the cannula, while the cannula enlarges the hole in the bone and is firmly anchored in this hole. Once the cannula is in its desired position, the probe may be removed by withdrawing it out of the end of the cannula not engaged with the bone.
The Cannula:
The cannula is a guiding tube that, in an embodiment, has a cutting edge on the distal end thereof. The cannula is essentially a long cylindrical tube which guides and holds the tamp in place while the tamp is being used to form the cavity. The cannula preferably has a handle to facilitate rotation and working of the cannula into the bone. More preferably, the cannula has a handle with a hole extending there through that is in alignment with and continuous with the hole extending through body. In one embodiment, the cannula handle is detachable. As described above for the probe handle, the detachable handle may be designed to be disposed of after completion of the surgical procedure. The handle of this embodiment may be fabricated from low cost polymer material so that replacement of the disposable handle is relatively inexpensive. Suitable materials and manufacturing methods for the handle of this embodiment are similar to those described above.
The cannula body preferably is tubular with the hole extending the entire length of the tube. The hole is advantageously, but not necessarily, circular. The hole is configured and adapted so that other tools, such as those described herein, may be inserted into the bone through the cannula hole. It is further preferred that the hole in the cannula allows the bone tamp to be freely rotatable. In an alternative embodiment, either the cannula, the tamp, or both, may be designed to impose a limited range of rotation. For instance, the cannula or probe may have stops that allow the tamp to be rotated within a certain range, but no further. In one embodiment, the limited range of rotation may be adjustable so that the range of rotation may be selected by the physician either before or during the surgical procedure.
In a preferred embodiment, the interior wall of the cannula defines an open cylinder having an inner diameter between about 3 mm and about 7 mm, more preferably between about 3 mm and about 6 mm, and most preferably between about 4.2 mm and about 5 mm. In one embodiment, the exterior wall of the cannula defines a cylinder that is between about 5 mm and about 9 mm. In a more preferred embodiment, the outer diameter of the cannula is between about 6 mm and about 8 mm, most preferably between about 6 mm and about 7 mm. In yet another embodiment, the exterior wall of the cannula defines a cylinder that is between about 4 mm to about 9 mm, more preferably between about 5 mm and about 6 mm, and most preferably about 5.4 mm.
The cannula may be made of a metal, for example a surgical steel alloy, an elastomer, or any other material suitable for surgical devices. The cannula can be constructed, for example, using standard flexible, medical grade plastic materials, like vinyl, nylon, polyethylenes, ionomers, polyurethane, and polyethylene tetraphthalate (PET). The cannula can also include more rigid materials to impart greater stiffness and thereby aid in its manipulation and torque transmission capabilities. More rigid materials that can be used for this purpose include stainless steel, nickel-titanium alloys (NITINOL(trademark) material), and other metal alloys.
In a preferred embodiment, the distal end of the cannula is adapted to cut through skin, tissue, and bone. In one embodiment, for example, the distal end of the cannula has a serrated edge. The end is advantageously circular to ease cutting into the bone. In addition, the cannula may also have a widely spaced thread disposed on the exterior body that assists in inserting the cannula into the bone. The thread may have a low-profile and a steep pitch for relatively quick advancement into and out of the bone. Thus, rotation of the cannula causes the threads to help advance the cannula into the bone. The threads also may be help anchor the cannula into the bone or facilitate removal of the cannula when desired. In one embodiment, the inside of the cannula and the probe may be threaded. This embodiment would provide for a more controlled advancement of the cannula with respect to the probe. Other tools, such as the bone tamps and cannula tamps described herein, also may be threaded so that their deployment inside the bone is more controlled. In an embodiment where the bone tamp is threaded, it is preferred that the pitch of the threads is relatively low so that the bone tamp does not significantly move in the axial direction while the bone tamp is being rotated to create a cavity in the bone.
The Tamp:
The tamp, or curette, is sized and adapted to pass through the cannula and into the cancellous portion of the bone. In one embodiment, where the tamping mechanism is then carefully expanded and rotated to form the cavity. The tamp has a body which is approximately advantageously, but not necessarily, a long cylinder. In one embodiment the an outer diameter or widest portion of the long body is between about 3 mm and about 7 mm, preferably between about 4 mm and about 6 mm, and more preferably between about 4 mm and about 4.5 mm at the point where the body enters the bone. In one embodiment, the diameter or dimensions of the long body is essentially unchanging along the length of the body. The body may be solid or hollow. In many embodiments, there is a groove along one side of the body, wherein a wire or a rod may pass. This wire or rod may be used to control the deployment of the tamping mechanism.
In a preferred embodiment, the tamping mechanism is sized to create cavities wherein the largest radial dimension of the flapper, or tip, measured from the axis of the body is between about 4 mm and about 24 mm, preferably between about 6 mm and about 20 mm, more preferably between 8 mm and 16 mm, and even more preferably between about 10 mm and 12 mm. Several tamping mechanisms having tips of varying lengths also may by provided so that the physician can determine the size of the cavity to create during the surgical procedure. In one embodiment, four tamps are provided with tip lengths of about 4 mm, about 6 mm, about 8 mm, about 10 mm, and about 12 mm. Other combinations of tamps having varying tip lengths also may be selected according to the desired sweep of the of the tamps.
This body and the tamping mechanism may be made of metal, for example a surgical steel alloy, an elastomer, or any other material suitable for surgical devices. The body and/or the tamping mechanism can be constructed, for example, using standard flexible, medical grade plastic materials, like vinyl, nylon, polyethylenes, ionomers, polyurethane, and polyethylene tetraphthalate (PET). The body can also include more rigid materials to impart greater stiffness and thereby aid in its manipulation and torque transmission capabilities. More rigid materials that can be used for this purpose include stainless steel, nickel-titanium alloys (NITINOL(trademark)), and other metal alloys.
The body typically has the appearance of a long rod or tube. The tamp is designed to have its distal end pass through a cannula and through a passageway cut into the bone. The tamping mechanism, which is on the distal end of the body, therefore also passes through the cannula and into the bone. The other end of the tamp body is controlled by the physician.
The body advantageously may have markings along its length so that the physician may quickly and easily determine the depth at which the tamp reaches into the bone. Preferably, the depth markings correspond to the length from the marking to the tip of the tamp when it is not deployed. That is, the markings indicate the distance to the tip before it is deployed. The physician is able to freely slide the tamp axially within the guide cannula to deploy it in the targeted treatment area. Alternatively, adjustable stops may be provided on the cannula, the tamp, or both in order to control the axial travel of the tamp or its range of rotation. The use of stops in this manner helps the physician to predetermine the size, length, and location of the cavity created. In addition, the adjustable stops also may allow the physician to gradually create the cavity within controlled parameters.
The physician-controlled end of the body contains a handle and a controlling mechanism by which the tamping mechanism may be deployed during tamping and retracted or un-deployed for removal of the tamp from the bone. While a motor may be used to effect rotation, it may be preferable in certain uses to manually rotate the tamp so that, for example, the physician may feel how easily the tamp is rotated. Manual operation of the tamp may provide a more tactile sense of the anatomy in and near the created cavity. In addition, manual operation of the tamp also may provide a sense of the degree to which the cavity has been completely created. If manual rotation of the tamp is resisted, for instance, the desired cavity size may not yet be created.
The tamp handle may be removable, but during manual operation of the tamp this handle should be fixed to the body. This handle is preferably sized and shaped to facilitate easy handling and rotationxe2x80x94that is, sized and shaped like a screwdriver handle. The handle also may be configured to indicate to the physician which direction the flapper is pointing. For example, the handle may have a flat surface on it in the direction where the flapper extends. Alternatively, the handle may have a texture, indentation, or other marking indicating the position of the flapper.
The handle also may be shaped like a pistol grip, where squeezing the grip effects a rotation of the tamp tip to its extended position. There may be a locking nut to hold the body of the tamp to the handle. Once the top is locked in position by the locking nut, the grip may be rotated to create the cavity in the bone. In addition, the locking nut may be configured so that the pistol grip may be partially squeezed and then locked in place so that the flapper is held in a position that is not fully extended. Other locking mechanisms may be used instead of a locking nut. In one embodiment, a ratchet mechanism is used to prevent the pistol grip from opening until the ratchet is released. The ratchet can have audible clicks that indicate to the physician the degree to which the flapper has been extended.
In one embodiment, the locking mechanism has markers that indicate to the physician the amount of sweep a flapper tip will provide when it is partially or fully deployed. Thus, a marker may indicate to a physician that the sweep of the flapper tip as it is rotated is only half the sweep of the flapper tip when it is fully extended. These markers may be provided on any portion of the tool. In one embodiment, the markers indicate the percentage of sweep that is achieved with respect to a fully extended tip. For example, the physician may select a setting for the flapper tip to provide only 50% of the sweep based on the marker indications. In another embodiment, the markers indicate the actual amount of sweep. In this embodiment, a physician may select the size of the cavity to be created by the marker indications. In yet another embodiment, the markers indicate the angle at which the flapper tip is deployed. Any or all of these embodiments may be used in combination with each other.
The tamp controlling mechanism controls the deployment of the tamping mechanism on the distal end of the body. Therefore, most embodiments of the tamp provide a control mechanism which runs alongside, or within, the tamp body. The controlling mechanism may move a rod, or extend a wire, or the like, wherein the rod or wire controls the degree to which the tamping mechanism is or may be deployed. In some embodiments, the controlling mechanism provides precise positioning of the tamp. In other embodiments, the controlling mechanism limits the range of motion in which the tamp may move, preferably gradually limiting the range of motion until the tamp is securely held in a single position.
Any method or device may be used to control the deployment of the tamping mechanism. In one embodiment, the controlling mechanism is a thread and a threaded collar, whereby rotating the collar relative to the handle of the tamp causes the tamping mechanism to expand, contract, or otherwise be deployed, such as by advancing or retracting the sheath around the tamping mechanism, advancing a rod or similar device to limit the range of motion of the tamp, or the like. Alternatively, the controlling mechanism may limit the expansion or contraction of the tamping mechanism.
Preferably, the thread has interruptions, such as flat sides cut at regular intervals, which interact with a locking pin and/or a bearing located within the collar. The locking pin or bearing, when in alignment with the interruptions of the threaded body, moves into the interruption to at least partially resist further turning of the collar. Preferably, the interruptions provide an audible and tactile click. As the collar is rotated further, the locking pin or bearing moves out of the interruption.
In an alternative embodiment, the thread does not have interruptions that provide an audible and tactile click. In this embodiment, the thread and collar have a continuous range of motion due to the absence of a locking pin or bearing moving in and out of thread interruptions as described above. In this embodiment, it is preferred that a locking or braking device can be applied to provide some resistance to rotation of the collar. The locking or braking device also may be designed to hold the collar in the position desired by the physician so that the collar does not slip or rotate out of position during use of the bone tamp to create a cavity.
In practice the controlling mechanism may in fact move the body of the tamp, relative to the handle such that the rod or wire, which may be fixed to the handle, appears to advance or retract when viewed at the distal end of the body. Alternatively, the controlling mechanism may cause the tamp to expand, contract, or otherwise be deployed by moving the tamp itself. In either example, the collar may be fixed to the handle in a manner that allows for rotation of the collar about the handle while restricting the collar from moving along the longitudinal axis of the handle.
In one embodiment, the tamp uses a directional tip, i.e., a flapper, attached to the distal end of the tamp as the tamping mechanism. The flapper may be hinged on one end to allow movement of the flapper relative to the body in one plane. In this embodiment, the flapper is hinged, and connected thereby, to the distal end of the cylindrical body so that the distal end of the flapper can be displaced out of alignment with the body so that when the flapper is rotated out of alignment with the body it provides a greater effective radius at the distal end of the tamp. Thus, when the tamp is rotated the flapper can displace cancellous tissue away from the tamp.
In a preferred embodiment, the flapper is hinged, and connected thereby, to the distal end of the tamp body so that the distal end of the flapper can displace itself out of alignment with the body to its maximum extent, and wherein the control rod when extended limits the effective radius at the distal end of the tamp.
In one embodiment, the flapper may move about the hinge, when unimpeded by the cannula or by the controlling mechanism, through an arc ranging from 0 degrees to between about 60 degrees and about 150 degrees, preferably to between about 80 degrees and about 120 degrees, and most preferably to about 90 degrees, with an angle of 0 denoting alignment with the tamp body. In a preferred embodiment, the range of motion of the flapper can be gradually limited by the control mechanism. For example, as the physician turns the collar as described above, the range of motion of the flapper is restricted from returning to alignment with the tamp until eventually the control mechanism securely holds the flapper in a single position. As mentioned above, it is most preferred that the final position of the flipper is about 90 degrees, although a final position in the ranges noted above may also be suitable.
In another embodiment, deployment of the flapper is controlled such that the flapper has little, if any, range of motion when the flapper is in any position. Thus, in this embodiment, partially turning the collar of the tamp results in partially extending the flapper out of alignment with the tamp body with little, if any, range of motion available to the flapper in any given position. This embodiment provides an advantage of allowing the physician to partially extend the flapper to create a cavity of a smaller diameter than when the flapper is fully extended. When the flapper is to be partially extended in order to gradually create the cavity, it is preferred that a locking or braking device as described above is used to help prevent the flapper from moving out of its desired position.
While the flapper may be configured and adapted to cut the cancellous tissue, compact or tamp it, or both, in one preferred embodiment the flapper has a blunt tip that primarily compacts the tissue. The blunt tip also may be used to effect reduction of a fracture. In vertebroplasty, for example, the physician may use the blunt tip to perforate the front surface of the vertebrae in order to effect a reduction. In addition, the physician may use the tip to move or reposition the endplate or other bony fragment to help restore the bone to its natural anatomy.
The flapper also may be curved or may have curved edges to further promote tamping back cancellous tissue when the tamp is rotated. In some applications, cutting may be preferred over tamping. Thus, the flapper may be configured and adapted to suit the particular application or desired result, such as by using a more aggressive flapper shape to cut tissue instead of tamp it. For instance, in one embodiment the edges of the flapper are designed to cut cancellous material when the flapper is rotated. A preferred flapper is a curved cup-type shape. The flapper may also be a cylindrical rod shape, or a flattened cylindrical or oval shape, a curved propeller-type shape, or a paddle shape. This flapper tip also may be rounded to minimize cutting.
In one embodiment of the tamp with a flapper having a gradually limited range of motion as described above, there is a rod which passes up a groove in the side of the tamp or, alternatively, up a groove inside the body of the tamp. In this embodiment, the rod is part of the controlling mechanism which, when in its retracted mode, does not interfere with the movement of the flapper. In its fully extended mode, the rod impinges on the flapper on one side of the hinge, which causes the flapper to be displaced from its alignment with the tamp body toward the other side of the hinge to its greatest extent. When the rod is in an intermediate position, the flapper can move from a point somewhat displaced from its alignment with the tamp body where the rod is impinging on the flapper to a point of maximum displacement from its alignment with the tamp body. It is preferred that the linkage is a single part to maintain simplicity in design and use.
Another tamp embodiment employs a expandable ring made from memory metal, i.e., a superelastic nickel titanium alloy such as NITINOL(trademark). The expandable ring has a preformed shape so that when the memory metal or NITINOL(trademark) body is retracted into the body of the tamp there is no expanded ring, and as the NITINOL(trademark) body exits from the body of the tamp an expanding ring is formed. The structure comprises a ribbon of resilient inert memory metal, which is bent back upon itself and preformed with resilient memory to form a ring. This expandable ring is the tamping mechanism.
The expandable ring may be formed into any desired shape. It also may be symmetrical about an axis or asymmetrical, depending upon the desired performance of the tamp. Moreover, the expandable ring may be formed such that a portion or side of the ring expands more than another so that the ring appears to be off-center from the longitudinal axis of the tamp body. In one embodiment, the ring is oval in shape, while in another the ring is D-shaped. In other embodiments, the expandable ring forms a polygon, which may have regular or irregular sides and angles.
In a preferred embodiment, the memory metal is in the form of a flattened ribbon. In another preferred embodiment, the edges of the expanding memory metal ring are blunted and/or curved to minimize cutting and to maximize displacement of the cancellous tissue during rotation. Manipulation of the ribbon, i.e., expanding and contracting as well as rotating, when inside bone tamps creates a cavity in the cancellous bone.
In one preferred embodiment, called the symmetrical ring embodiment, the expandable ring when in its fully expanded position forms a ring-like structure with a point on the distal end of the body. In a variation of this embodiment, the ring forms a hexagonal-type structure with one point on the distal portion of the ring and a second point near the body of the tamp. In another embodiment, the ring when in its fully expanded position forms a circular or oval structure, or flattened version thereof. In a third embodiment, the ring forms a rounded triangle, where the radius of each corner of the triangle is beneficially at least 3 mm. In these embodiments, the deployment of the ring can be affected by either a wire which allows deployment and retraction of the ribbon outside the body of the tamp, wherein feeding wire in expands the ring and pulling wire out retracts the tube, or in the case of preformed tubes by pushing the tube outside the body, for example with a rod, wherein as more of the ribbon extends past the body of the tube, the ring or other structure will grow or expand in size or length. The option of feeding and retracting wire is preferred.
In a particularly preferred embodiment, the ring forms an asymmetrical ring. In practice, this ring may form a shape of a xe2x80x9cDxe2x80x9d. In this embodiment, one end of the ribbon forming the ring may be attached to a rod while the other end runs back towards the handle. The controlling mechanism in this embodiment controls the expansion of the loop. Of course, the xe2x80x9cDxe2x80x9d shape of the asymmetric loop is pre-formed. In its fully withdrawn position, the ring is sufficiently compact to fit into the tamp body.
The cannula, tamping body, and/or tamping mechanism may have disposed thereon one or more radiological markers. The markers are made from known radiopaque materials, like platinum, gold, calcium, tantalum, and other heavy metals. The markers permit radiologic visualization of the loop structure, tamp body, and/or cannula within the targeted treatment area.
The systems and methods embodying the invention can be adapted for use virtually in any interior body region, where the formation of a cavity within tissue is required for a therapeutic or diagnostic purpose. The preferred embodiments show the invention in association with systems and methods used to treat bones. The systems and methods which embody the invention are well suited for use in this environment. It should be appreciated that the systems and methods which embody features of the invention can be used in most bone structure, including but not limited to the vertebra.
The invention also provides directions for using a selected tool according to a method comprising the steps of deploying the tool inside bone and manipulating the structure to cut cancellous bone and form the cavity. The method for use can also instruct filling the cavity with a material, such as, e.g., bone cement, autograft material, allograft material, synthetic bone substitute, a medication, or a flowable material that sets to a hardened condition.
The cavity may be irrigated and/or aspirated to clear the cavity prior to delivery of bone filler material. In addition, inflatable devices, such as a surgical balloon or similar device, may be used when treating the bone. These methods and devices are further described in pending U.S. application Ser. No. 09/908,899, entitled xe2x80x9cInflatable Device and Method for Reducing Fractures in Bonexe2x80x9d, which is incorporated by reference herein in its entirety.